The chilling manifesto that police say Elliot Rodger sent to his therapist before killing six people and then himself has highlighted the “duty to protect,” part of a California law that requires psychotherapists to warn police about violent threats.

Rodger, a 22-year-old college student, emailed his therapist a link to the 137-page manifesto before the deadly rampage, close family friend Simon Astaire told ABC News. The therapist then called Rodger’s mother, Chin Rodger, at 9:17 p.m. PT on Friday.

"Have you gotten Elliot's email?" the therapist said, according to Astaire. "I think you should see it."

The email had been sent to "several other mental health professionals and what appeared to be family,” a police spokesman told ABC News. One counselor opened the email at 10:00 and called police minutes later, but it was too late. Rodger had already opened fire outside a Santa Barbara, California, sorority house, according to police.

Under California law, psychotherapists have a “duty to protect” and are required to report “a serious threat of physical violence against a reasonably identifiable victim” to local law enforcement within 24 hours. The law, which used to require therapists to “immediately report” the identity of a threatening patient, was amended in October 2013 to better define the timeline to one full day.

"'Immediately' is undefined, and changing the standard to '24 hours' will add certainty and consistency to the reporting,” the bill to amend the law read.

Calls to the office of state Sen. Ted Gaines, who introduced the bill, and Tom Ammanio, chair of the Assembly Committee on Public Safety, were not immediately returned today.

The law aims to balance public safety with a patient’s right to privacy -- a delicate line that has been the subject of scrutiny in light of a slew of mass shootings. Even the federal government has weighed in with clarification of the Health Insurance Portability and Accountability Act, or HIPAA, stressing to healthcare providers that the patient privacy rule “does not prevent your ability to disclose necessary information about a patient to law enforcement, family members of the patient, or other persons, when you believe the patient presents a serious danger to himself or other people.”

“If a mental health professional has a patient who has made a credible threat to inflict serious and imminent bodily harm on one or more persons, HIPAA permits the mental health professional to alert the police, a parent or other family member, school administrators or campus police, and others who may be able to intervene to avert harm from the threat,” Leon Rodriguez, director of the U.S. Department of Health and Human Services’ Office for Civil Rights, wrote in a January 2013 letter to health care providers.

The name of Rodger’s therapist has not been released. It’s also unclear at what time he or she received the email linking to Rodger’s manifesto.